I've found that often when trying to use Google Maps Bicycle for route planning that Google will divert quite a ways at times to get me onto a bike path or trail.

Riding dirt or gravel roads may not be too bad but sometimes those roads are a lot hillier or slower to ride on than a paved road. It depends on what you're iding, what you're carrying and if your trip is to just get somewhere and thus you want the fastest route to get you there. Sometimes too the satelite view will let you know if a road is gravel.

Perhaps Google plus a paper map?

Cheers